The changes that the male body undergoes during puberty are complex and largely driven by hormones. Through this lesson, you will explore the role that various hormones play in the physical and behavioral changes that occur from puberty to maturity.

What Are Hormones?

As humans age, they go through several important physical and psychological developmental stages. In some cases, we don't really notice that these changes are occurring, but there is one stage that everyone recognizes and few remember fondly: puberty. In boys, puberty generally begins around 9 years of age and lasts until they've reached adulthood (around 18 to 20 years old). This period is filled with significant and obvious physical changes, most of which are driven by hormones.

Hormones are a substance that we produce through our body's glands. Each hormone serves a very important purpose in our development and health. For example, if you're in a stressful or dangerous situation, your body produces a hormone called adrenaline, which dilates your air passages and directs blood to your muscles. In this case, adrenaline is preparing your body to move with speed and strength so that you can either fight the danger or run away.

During puberty, various hormones work in a similar way, although this time they're preparing the body and brain for adulthood. In boys, this includes, among other things, growing taller, gaining weight, and experiencing a deepening of the voice, all of which are visual indications of maturity.

Onset of Puberty

In boys, the first stage of puberty begins when the brain begins sending gonadotropin-releasing hormone (GnRH) to the pituitary gland. GnRH sends a signal the testes, which begin to enlarge as they produce sperm cells.

The anterior pituitary gland plays a critical role in hormone production and release during puberty.

In addition to signaling the testes, GnRH causes the pituitary gland to release two other hormones into the blood stream: luteinizing hormone (LH) and follicle-stimulating hormone (FSH). Once activated, these hormones trigger some of the most significant changes in the body, particularly by starting the production of testosterone, a steroid hormone that is responsible for, among other things, the growth of the testicles and penis, development of muscle mass and bone density, and the production of body hair.

Physical Changes to the Body

In general, physical changes to the body happen gradually and might not be immediately apparent. During puberty, however, physical changes happen rapidly once the process is initiated by GnRH. During what is commonly referred to as a 'growth spurt', for example, the anterior pituitary gland releases a hormone known as growth hormone, which stimulates, among other things, physical development of bones, cell reproduction, and the enlargement of internal organs.

In addition to the development of muscle mass and bone density that accompany getting taller and gaining weight, the body undergoes other important changes as a result of hormones. For example, testosterone, which drives puberty in boys, causes the larynx to grow and the vocal cords to stretch as they become thicker. Until the body adjusts to changes in the larynx, a boy's voice may crack or squeak from time to time as the larynx gets used to its increased size. This process begins at the onset of puberty and is usually completed around the late teens or early 20s, when the individual has reached adult size.

Along with other hormones, growth hormone contributes to the development of muscle mass, bone density, and organ growth.

Although certain hormones play different and sometimes larger roles in the development process, it's important to remember that they all work together to keep the processes going smoothly. For example, during puberty, GnRH stimulates other hormones like testosterone and FSH. Were one of these hormones to be deficient or not work properly, the whole delicately balanced system would be disrupted and cause developmental problems.

A good example of this is seen in people who have testosterone deficiencies. In this case, the limited testosterone may cause underdeveloped testes, which can affect sperm production and also lead to other problems like depression.

Behavioral Changes

In a basic sense, the changes that occur during puberty are intended to, among other things, prepare the body for reproduction. Things like a deeper voice and body hair are physical signs that a person has reached maturity and is now capable of sexually reproducing. Of course, there's a great deal more to the process than just physical changes, and those that occur in the brain can be a lot more complicated.

The hormones that trigger physical change are also responsible for the major changes in emotions, feelings, and behaviors. After all, if the main purpose is to prepare the body for reproduction, then it naturally follows that one will have to want to have sex. In both sexes, this is referred to as a sex-drive or libido and its strength varies from person to person. For boys and young men, this is the result of testosterone working with a neurotransmitter known as dopamine. Working together, these two stimulate sexual arousal in the brain and produce a desire to have sex.

For men, sexual attraction and sex-drive are incredibly strong during this time, reaching their peak at about age 16 and slowly declining over a long period of time. While sexual attraction and libido are incredibly strong during puberty, there are other emotional or behavioral changes that occur as a result of hormones. Increased assertiveness or aggression, for example, is due in part to increased levels of testosterone; however, researchers remain divided as to how significant testosterone is in that process.

Lesson Summary

Between the onset of puberty around age 9 and adulthood in the early 20s, boys' bodies undergo considerable changes due to a flood of hormones. This process is triggered by gonadotropin-releasing hormone, which releases several hormones into the blood. Of these, testosterone is the most significant, as it is responsible for, among other things, the production of sperm, hair growth, and the development of muscle mass.

Although some hormones play a greater role in the development process from child to adult, they generally work together. Growth hormones, for example, stimulate other hormones to aid the growth of bones and organs, while dopamine acts with testosterone to increase sex-drive, all of which becomes regulated as the body reaches maturity.

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